That's just the luck of the draw, though. Yellow Fever happens to be amenable to life-long immunity. COVID (may) not be. Had the situation been reversed, you'd

That's just the luck of the draw, though. Yellow Fever happens to be amenable to life-long immunity. COVID (may) not be. Had the situation been reversed, you'd have had to get Yellow Fever vaccinations a lot more often if you were travelling into those regions, and the COVID situation would be one-and-done. It just happens that this is the way it worked out, instead. There's nothing dystopian about this.